Bolted Joint Strength of Graphite/Epoxy Laminates Subjected to Biaxial Loading Conditions

Abstract

Bolted graphite/epoxy plates were subjected to in-plane biaxial loading. Cruciform shaped samples were used. Testing was performed on a biaxial machine developed and built at Concordia University. Four arms of the cruciform sample were independently loaded. Different lateral loads were applied along one direction. Along the other direction, load was applied on one arm while the opposite arm was held in the grip without applied load. This opposite arm measured whatever load that was bypassed around the constrained bolt hole. Acoustic emission was used to detect the onset of failure. There was a correspondence between the time at peak acoustic emission activity with the change in slope of the bypass versus applied load curve. Results show that there is a significant decrease in joint strength with the application of the lateral load. This effect is more severe for plates with smaller size hole (6.35 mm dia.) as compared to plates with larger size hole (19.05 mm).